Windows: If you have a spare USB drive or SD card lying around, use RMPrepUSB to turn it into a PC troubleshooting tool or a way to install a new OS without burning a disc. You can use the tool to format and partition any storage device, load it up with ISOs or other disk images, and then multi-boot when you need to. »6/17/13 4:30am 6/17/13 4:30am

Android (Rooted): Whether you're troubleshooting a problematic PC or you just prefer working in your own OS with your own tools, keeping a Linux boot CD or USB key is a great way to take a customized system with you anywhere you go. With DriveDroid, you don't need to bother with media, and can use the gadget you… »3/15/13 4:00am 3/15/13 4:00am

If you're particularly indecisive about your regular operating system, or just want access to all three for testing purposes, Wired's How-To Wiki has the details on getting a triple-boot system (or beyond) working with free software tools. »11/03/09 7:00am 11/03/09 7:00am